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It's had a rough ride from the start with opponents to the High Speed 2 rail link calling the 50 billion pound project a white elephant. And just this week a parliamentary report called for the line to be abandoned.

But today the Prime Minister launched what he called the "fightback" by the government over the scheme. Phase One of HS2 would cut through environmentally sensitive parts of the Oxfordshire and Buckinghamshire countryside linking London with the midlands.

And today a report was released claiming the project would boost Britain's economy by 15 billion pounds a year.

Video: The Transport Secretary has argued the economic case for the proposed High Speed Two rail route through Oxfordshire and Buckinghamshire.

Patrick McLoughlin insists without HS2 key rail routes would be "overwhelmed" by rising passenger numbers. But, earlier this week, the Public Accounts Committee said it would cost more than originally estimated and wouldn't bring the promised economic benefits.

Ministers are arguing HS2 will provide an annual boost of £15 billion to the UK economy. Credit: PA

HS2 will provide a £15 billion boost to the UK economy every year after it is built, the Government claims.

Transport Secretary Patrick McLoughlin will argue the network will relived the pressure on Britain's transport system and insist the project will be completed within its £42.6 billion budget.

"The main reason we need HS2 is as a heart bypass for the clogged arteries of our transport system," McLoughlin will say.

Ministers are attempting to bolster support for the train link, which will connect London with Birmingham, Leeds and Manchester, after it came in for withering attacks from the influential Public Accounts Committee.

The Transport Secretary is expected to argue the economic case for the proposed High Speed Two rail route through Oxfordshire and Buckinghamshire today. Patrick McLoughlin insists that, without HS2, key rail routes would be 'overwhelmed' by rising passenger numbers.